Heat-reflecting glass and method for manufacturing the same

ABSTRACT

On the surface of a glass substrate is formed by hydrolysis or thermal decomposition a light-transmissive film of a metallic oxide having a refractive index higher than that of glass and colloidal particles of metallic palladium or of metallic palladium and metallic gold, said particles being uniformly dispersed in said metallic oxide. The film has the transmission color of bluish gray, neutral gray or yellowish gray and is capable of reflecting about 30 to 40 percent of solar energy radiation. The film also has superior mechanical strength and chemical stability, so that glass having such a film can be successfully used as a heat-reflecting glass in single-pane installations.

United States Patent 15 3,660,137 Furuuchi et al. 5] May 2, 1972 [54]HEAT-REFLECTING GLASS AND 3,407,081 10/1968 Ballard ..117/124 x METHODFOR MANUFACTURING THE 3,400,006 9/1968 Berning et a1. ...1 17/33.3 SAME3,440,062 4/1969 Hoffman ..1 17/160 [72] Inventors: Shigemasa Furuuchi;Katsuaki Aikawa, HER P BLICATI NS both of Kanagawa-ken Japan Hopper, Howto Apply Noble Metals to Ceramics," Ceram- [22] Filed: June 13, 1969 10Industry, 6/63 V01. 80, No. 6 pp. 65- 68 [21] Appl' 8329 PrimaryE.raminerWilliam D. Martin Assistant Examiner-Mathew R. P. Perrone, Jr.[30] Foreign Application Priority Data Auorney-Kurt Kelman une 2 1968Japan 43/43597 ABSTRACT US. Cl. l l R, on the surface of a glasssubstrate is formed hydrolysis o 1 17/124 H, 1 17/124 C, 1 17/160 R,161/196, 350/1 thermal decomposition a light-transmissive film of ametallic [51] Int.C| ..C03c 17/10 oxide having a refractive index higherthan that of glass and [58] Fleld Search 17/33'31 160; 350/1; vcolloidal particles of metallic palladium or of metallic palladi-161/196 um and metallic gold, said particles being uniformly dispersed56 f d in said metallic oxide. The film has the transmission color of l1 Re erences bluish gray, neutral gray or yellowish gray and is capableof UNITED STATES PATENTS reflecting about 30 to 40 percent of solarenergy radiation. The film also has supenor mechanical strength andchem1cal 2,768,909 10/1956 Haslam ..l l7/33.3 X Stability, so that glasshaving Such a film can be f ll 31069-301 12/1962 Buckley used as aheat-reflecting glass in single-pane installations. 3,087,831 4/1963Browne ..1 17/124 X 3,266,912 8/1966 Murphy ..1 17/124 X 6 Claims, 2Drawing Figures I OO Z 9 (D Q E (I) Z II 1,-

WAVELENGTH IN PERCENT mgmgmme ISIE 3, 660, 1 37 I00 F/ so TRANSMISSIONIN PERCENT 3G0 500 TOO 900 I IOO I500 I500 WAVELENGTH IN PERCENTREFLECTION IN PERCENT 300' 660 7C0 960 1 H00 1300' I500 WAVELENGTH INPERCENT INVENTORS iHIGEMA6A mauucm BY KMsu/m AIKAWA HEAT-REFLECTIN GGLASS AND METHOD FOR MANUFACTURING THE SAME BACKGROUND OF THEINVENTION 1. Field of the Invention This invention relates to aheat-reflecting glass having on the surface a film capable of reflectingand shielding out the thermal energy contained in light rays andparticularly in solar radiation, said film having been formed on eithersurface, on one surface only or in a localized area of the surface ofthe glass substrate, and a process for the manufacture of such glass.

2. Description of Prior Art As sheet glass for use as window panes orWindshields, in the openings in buildings and other large structures aswell as in vehicles such as automobiles, there is known aheat-reflecting glass which is capable of reflecting the thermal energyof solar radiation and preventing inflow of the heat.

By current standards, a glass sheet on which a thin continuous film ofmetallic gold has been deposited by vacuum deposition is generallyaccepted as the best heat-reflecting glass. However, metallic goldadheres to glass surfaces only with considerable difi'iculty and theresulting film leaves much to be desired in mechanical strength andhardness.

For this reason the metallic gold film must be protected by anadditional glass member. Such a heat-reflecting glass must therefore bemanufactured or put to use in the form of laminated glass or as a doubleglazed glass unit. This entails considerable increases in both weightand bulk of the product, and, accordingly, increased production cost.

Furthermore, application of the vacuum deposition technique to theformation of a thin film involves the use of large-scale equipment andcomplicated procedures, which result in low production efficiency.

The same disadvantages are encountered in the production and use ofother types of heat-reflecting glass possessing continuous films ofother metals such as copper, platinum and silver.

Some of the above problems are solved by copending U.S. patentapplication Ser. No. 55l,566, filed May 20, l966, replaced bycontinuation application Ser. No. 866,100, filed Oct. 6, 1969. Thisapplication relates to a heat-ray reflecting film deposited on glass byhydrolysis or thermal decomposition, said film being composed of ametallic oxide having a refractive index higher than that of glass, suchas TiO Ta O W ZrO ThO SnO,, or Nb O and metallic gold and/or metallicplatinum which are uniformly dispersed in said metallic oxide inmicroscopically divided form. This film is superior in mechanicalstrength and chemically stable, so that it can be used asheat-reflecting glass and particularly as solar energy shielding glass.However, the use of extremely expensive platinum is not economicallyadvantageous.

SUMMARY OF THE INVENTION The primary object of this invention is toprovide a heatreflecting glass which has a film of the described type onthe surface, said film not only possessing an excellent heat-reflectingperformance but also being highly resistant to abrasion, scratching ordegradations even upon direct exposure to the outside atmosphere.

Another object of this invention is to provide a glass having on thesurface a film with the transmission color of neutral or orangy gray, aswell as excellent coloring property, superior heat-ray reflectingperformance and excellent mechanical and chemical properties.

Still another object of the invention is to provide a process forproducing a heat-reflecting glass of the described type without resortto a special atmosphere, intricate equipment and complicated processingtechniques.

Other objects and advantages of the invention will become apparent fromthe following description.

It has been found that the above-mentioned objects of the invention maybe accomplished by dispersing uniformly metallic palladium in amicroscopically divided state into a film of a metallic oxide which hasa refractive index higher than that of the glass substrate on which itis being deposited.

The heat-reflecting glass according to this invention comprises a glasssubstrate, a light-transmissive film disposed on the surface thereof,said light-transmissive film being composed essentially of a metalicoxide having a refractive index higher than that of substrate glass andmicroscopically divided particles of metallic palladium which areuniformly dispersed in said metallic oxide.

Hydrolysis or thermal decomposition is the most advantageous method fordepositing such a film on the surface of glass. Thus, a compound whichwill form said metallic oxide upon heating and a compound capable ofliberating metallic palladium on heating are dissolved in a solvent, andthe glass substrate is coated with the resulting solution. This coatedglass is then baked, whereupon a heat-reflecting film of the describedtype is formed on the surface of the glass.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 show the spectraltransmission and reflection characteristics, respectively, of aheat-reflecting glass embodying the principles of this invention atwavelengths in the visible to near infrared region.

Referring to FIGS. 1 and 2, the percent transmission and reflectionvalues are plotted on the vertical axes, against wavelengths in my onthe horizontal axes. Figures accompanying the curves correspond to theserial numbers of glass samples described in Example I which appearshereinafter.

DESCRIPTION OF PREFERRED EMBODIMENTS The heat-reflecting film accordingto this invention consists essentially of a metallic oxide having arefractive index higher than that of glass and metallic palladiumdispersed in said metallic oxide uniformly and in a microscopicallydivided state. This film features the transmission color of yellowish ororangy gray but its coloring property, that is to say, reduction inlight transmission per unit thickness is relatively low.

In order to enhance the coloring property of such a film, we havediscovered that the presence of metallic gold along with metallicpalladium is highly beneficial. The amount of metallic gold for use inthis application should be about 0.1 to about 20 times the amount ofmetallic palladium by weight and, preferably, from about 0.5 to aboutfive times. The film containing both metallic palladium and metallicgold has the transmission color of yellowish gray to neutral grayfurther to bluish gray in the order of an increasing gold content.

The mechanism by which this invention produces a film of superiorheat-reflecting performance remains yet to be fully elucidated, but itis believed that this improved performance is a synergistic resultbetween the light interference effect of the metallic oxide having arefractive index higher than that of glass and light-absorbing effect ofthe metallic particles of palladium -or of palladium and gold which aredispersed uniformly in the oxide matrix in a microscopically divided orcolloidal state.

It has been found that when use is made of a metallic oxide having arefractive index lower than glass as a matrix material in which saidmetallic particles are dispersed, the light interference effect of thematrix impedes the heat-reflecting performance of the metallicparticles.

In accordance with this invention, therefore, the matrix is composedessentially of a metallic oxide having a refractive index higher thanthat of glass. As specific examples of the metallic oxide which has arefractive index higher than that of glass and accordingly can besuitably employed as a principal component of the matrix, it has beenfound from studies in optical properties, adhesiveness to glass,mechanical properties and chemical stabilities that TiO Ta O W0 ZrO ThOSnO and Nb O are particularly suitable. These metallic oxides can beused either singly or in combination, but among them TiO is best by anyof the above criteria.

While there is no specific restriction upon the amount of the metalliccomponent (metallic Pd or metallic Pd and Au) contained in the filmaccording to this invention, the preferred amount is 2 to 60 percent byweight (about 0.4 to 23 percent by volume) and, for better results, 4 to50 percent by weight (about 0.8 to 17 percent by volume). If theproportion of the metallic component is below the lower limit, theheat-reflecting performance of the film will be inadequate, whileproportion in excess of the upper limit will result in inadequateadhesiveness and mechanical strength.

In addition to the metallic oxide which is used as a principal componentof the matrix, it is permissible to incorporate minor proportions ofsuch additives as SiO and/or Bi O Addition of SiO makes the surfaces ofthe film harder and smoother, while addition of Bi O leads to a reducedtransmission of ultraviolet rays and, accordingly an improvedultraviolet shielding effect. The additives can be added in amounts from0.5 to 30 percent by weight and, for better results, from 2 to percentby weight, based on the metallic oxide.

The following description deals with a process for the formation of thefilm described hereinbefore on a glass substrate.

In the first place, a coating solution is prepared. A soluble palladiumcompound and, if required, a soluble gold compound are dissolved in asolvent, together with a soluble metallic compound which is capable offorming a metallic oxide which is to constitute the above-mentionedmatrix. The surface of a glass substrate is coated with the abovesolution, and the coated glass is baked at a temperature from about 400C to the softening point of the glass. In the process the solvent isevaporated and the palladium compound is decomposed to yield metallicpalladium (and metallic gold), while the other metallic compounddecomposes into the corresponding metallic oxide.

In this manner, a film in which the metallic component is uniformlydispersed as colloidal particles within the metallic oxide is formed inintimate contact with the surface of the glass substrate.

The palladium compound to be used in the preparation of said solution ispreferably the chloride of divalent palladium, although other solublesalts of divalent palladium such as the nitrate and sulfate, palladiumresinate, and palladium-alkyl mercaptides such as palladium-ethylmercaptide can likewise be employed. The gold compound is preferablychloroauric acid, but such other compounds as'gold-alkyl mercaptides,e.g. gold-ethyl mercaptide, gold-propyl mercaptide, as well as alkylgold halides, e.g. diethyl monobrom'o-gold can be employed as well.

The compounds, which on heating can become said metallic oxide, e.g. theoxide of Ti, Ta, W, Zr, Th, Sn, Nb, Si or Bi, include such metallic acidesters as tetra-butyl titanate, tetraisopropyl titanate, ethyl silicate,halogenides, nitrates, acetates, sulfates, complex salts and the like.

While those compounds of palladium and of gold, as well as the metallicoxides mentioned above, can be dissolved in water, use of aqueoussolutions is not desirable from the standpoints of solution stabilityand the wettability of the glass surface.

In accordance with the invention, the above-mentioned compounds arepreferably dissolved in organic solvents such as alcohols, acetone,esters, alicyclic compounds, and aromatic compounds, or for betterresults, in lower aliphatic alcohols such as methanol, ethanol,propanol, butanol and the like.

It is permissible to incorporate in the solutions suitable additives forsuch purposes as adjusting the wettability of the glass surface with thesolution, improving the homogeniety of the solution and adjusting theviscosity or pH of the solution.

In preparing a solution that will yield a film containing both metallicgold and metallic palladium, the concentration of the gold compound, asAu (hereinafter called Au concentration), in the solution is preferably0.1 to 20 times by weight relative to the concentration of the palladiumcompound (hereinafter called Pd concentration). While the Au compound inthe solution is decomposed to yield metallic gold when the glass coatedwith the solution is heated, it is presumed that, in this process, theAu serves as a growth catalyst or nucleating agent for the metallicpalladium particles being deposited on the glass surface.

Stated differently, in the course of heating, microscopically fineparticles or nuclei of metallic gold are first formed and, then, aroundor in the vicinity of those particles, metallic palladium particlesprecipitate and grow. The metallic particles produced in this manner areapparently different from the particles of palladium alone in opticalproperties, having in particular, an increased light absorption.

For the above reason, it is believed that use of a solution containingthe gold compound yields a film which features a good coloring property,that is to say, a film which has a lower transmission and a deep color.

If the gold concentration of the solution is lower than 0.1 timesrelative to the palladium concentration, there will be no improvement incoloring property, while if the gold concentration is beyond 20 times,the transmission color of the resulting film will be blue. Thus, thosetwo extremes are undesirable. For better results, the above-mentionedproportion should be further limited to the range of about 0.5 to about5 percent.

The concentration of the palladium compound in the solution vary ratherwidely, but if the concentration is too low, the transmission color ofthe film will be too faint. Therefore, the concentration of thepalladium compound, as Pd, should be at least 0.4 g/l and, usually,about 2 g/l to 20 g/l.

It is to be understood that the concentration of the abovementionedother compound in the solution should be selected according to theexpected proportion thereof in the form of oxide in the film.

The solution prepared in the described manner is used in the coating ofglass. Thus, a glass sheet is dipped in the solution and, then, slowlyraised out of the solution, whereby a homogeneous layer of the coatingis formed on the surface of the substrate. The coated glass is thendried at room temperature or at an elevated temperature from to 200 C.It is to be understood that any other similar coating technique such asspraying or roll coating can also be utilized with success.

The glass is then heated at temperatures over about 400 C and below itssoftening point, preferably from 450 to 800 C, for a duration of about10 minutes. The thickness of the resulting film can be adjusted asdesired by regulating the concentrations of the solutes (i.e. the Pdcompound, Au compound and other compound) in the solution and the amountof deposition of the solution on the substrate. For practical purposes,the film preferably ranges, in thickness, from about 100 A to 1,500 Aand, for better results, from 300 A to 800 A.

The film thickness should not exceed 1,500 A, for an undesirableiridescent color will then be produced in the film. On the other hand, afilm less than 100 A in thickness does not possess a sufficiently highheat-reflecting performance.

In carrying the invention into practice, the metallic oxide film whichcontains metallic particles (hereinafter called main film) may be usedin combination with one or more different types of films to produce adouble-layer or multiplelayer film on the glass surface.

For instance, through the deposition of an intermediate layer(underlayer film) composed solely of metallic oxide (e. g. TiO Ta O W0ZrO ThO SnO or Nb O between the main film and the glass surface, it ispossible to improve the mechanical strength or/and adhesiveness of themain film.

And when the under-layer is made predominantly of a metallic oxide, e.g.SiO which has a refractive index lower than that of glass, theheat-reflecting performance and visible transmission characteristic ofthe product are improved through a light interference effect among theunder-layer film, the glass and the main film which has a higherrefractive index.

To obtain an under-layer film of the type described, the substrate glasssurfaceis coated with a solution containing the 3,660,137 6 requiredmetallic compound and the resulting coated glass is synergistic resultof metallic palladium and gold. Comparison dried and/or heated andfinally baked. Thereafter, the glass is of the glass sample No. l or No.6, which contained only further treated with a main film formingsolution to obtain the metallic gold or metallic palladium alone, withglass samples main film S a f fi layer I No. 3 through No. 5, whichrespectively have on either surface The glass substrates to whlch 311$Invention can be pp 5 a film containing both metallic palladium andgold, shows t0 a n ag include, f0r p Soda-lime g Potash reductions inlight transmission for the latter samples, E bol'osilicate g bariumCrown g quartz g evidencing the improved coloring property of glass dueto the other transparent, opaque or colored glass, heat-absorbingconcurrent presence of metallic palladium and metallic gold.

glass and the like, irrespective of their compositions and types Th h il d h i l properties of the films of the As regards the shape of theglass substrate, this invention six glass samples prepared in the abovemanner are as follo s. can be applied to any shape of glass, Such as plne Sheet glass, Mechanical strength of a film: Neither the pen tip nor arazor curved sheet glass, optical lenses, spectacle lenses and the bl dld damage th film On Mohs s ale, the hardness like.

The following examples are given to further illustrate this invention,it being understood that the i means limited thereto.

values of the films could be placed between 5 and 6 After a scratchresistance test in which each sample was mention is y no moved back andforth against a pencil eraser which contained glass powder under a loadof 633 g/cm, the increase in visible transmission of the film was onlyless than 1 percent.

Chemical stability of the film: As a weathering test, each Six differentsolutions were prepared according to the for- Sample was treated in aWeflther-O-Met e1' for 2,000 hours mulas shown in Table 1. Sample No. lwas a control solution (Corresponding to 10 years of atmosphencexposure) There prepared by dissolving tetra-isopropyl titanate (Ti(CH,O) was no detectable change in color of the film in the visible reandhydrated chloroacuric acid (HAuCL-xI-I O; the value of x 8 Example 1unavailable, but the acid contains 50 percent by weight of Au) when theSample was f f water or N oxalic acid in a mixture of ethanol andn-butanol. The other samples, at C for 5 hours, no change color wasobserved numbered 2 3 4 and 5 contained various amounts of The abovedata indicate that the heat-reflecting glass Of this um hl id pdcl y I Sl No 6 h terraisopropyl invention can be successfully used insingle-pane application. titanate and palladium chloride were dissolvedin the same sol- Example II TABLEI Six different solutions were preparedaccording to the formulas shown below in Table III.

Ingredient Example No.

l 2 3 4 5 6 TABLE III Ti(OC H,) 18g 18g 18g 18g 18g lSg I t I I am, 4 r02.0g 3.0g 4.0g 4.0g 7 8 g e M 10 11 12 HAuCL'xl-I O 3.9g 6.0g 6.0g 6.0g6.0g Ethanol 67cc 67cc 67cc 67cc 67cc 67cc n-Butanol l33cc 133cc 133cc133cc 133cc 133cc 40 Talc]5 4 gr NbCl, s g Th No, -4H,o 10 g ZYC 4 5 8Soda lime glass sheets, 3 mm thick and 30 by 30 cm, were 5,101 5 gthoroughly washed and dried. Then, the sheets were dipped in L; 7 g thesolutions and slowly raised out of the solutions at the rate HAUCIIIHzO3 8r 3 gr 3 8r 3 3 3 f b 15 I b0 h If f h l dCl 1 gr 1 gr 1 gr 1 gr 1 gr1 gr 0 a out cm/mmute. n t is manner, t su aces o eac SKOCZHO ICC cc 1Cc 1 cc 1 Cc 1 Cc glass sheet were evenly coated with the correspondingsolu- HNO;, 1 cc 1 cc 1 cc 1 cc 1 cc 1 cc tion. The coated glasssurfaces were dried by heating at 200 C Ethanol 33 cc 33 cc 33 cc 3 c 3cc 33 cc for 10 minutes, at the end of which time the sheet was heatedniBumnol 67 cc 67 cc 67 cc 67 cc 67 CC 67 cc in a muffle furnace at 680C for 10 minutes, whereupon the films were firmly baked onto thesurfaces.

The thickness of each film so formed was about 500 A. The The solutionsdesignated No. 7 through No. 12 corspectral transmission and reflectioncharacteristic curves of responded to the solution designated No. 3 inthe above Table those six glass samples are reproduced in Figs. 1 and 2,respec- I in which the Ti(OC H had been replaced by other metallictivelyv compounds capable of forming metallic oxides on heating andTable II below show the solar energy transmissivity (T small amounts ofadditives, i.e. ethyl silicate Si(OC l*l and Solar gy reflectivity (RE):Visual transmissivity y) and HNO had been further incorporated. It is tobe understood visual reflectivity R all in percentage, for thosesamples, as that HAUCh'XH O contained 50 percent by weight of Au.calculated from the above spectral transmission and reflection In theame manner as Example I, a film about 500 A thick curves. was formed oneither surface of each glass sheet 3 mm thick TABLE ll l-imuuplv Xi l 'l3 4 5 li 'lrrmsmissinn colon. s tlrr'rnisli liluis'll Neutral OrungyOrungy Yvllowish blue. gray. gray. gray. gray. gray.

ll. 11: percent r .r s 40 40 35 33 32 55.

The glass sample designated No. l, which had a TiO, film and 30 by 30cm.

containing particles of metallic gold alone on either surface, Theresulting six glass samples had the transmission color of showed thetransmission color of greenish blue. In contrast, neutral gray and theirspectral transmission and reflection the samples designated No. 2through No. 5 had the transmischaracteristics were substantiallyidentical with those of the sion color of substantially neutral gray,thus attesting to a above-mentioned No.3 sample. Thus, the values of Tranged from about 35-40 percent, R values from about 30 to 35 percent, Tfrom about 26 to 30 percent, and Rv from about 30 to 35 percent. Themechanical strength and chemical stability values of those samples werealso substantially identical with those of the No. 3 sample.

Example Ill Two different solutions were prepared according to theformulas shown below in Table IV.

in those solutions, tetra-butyl titanate was used as the Ti compound,and organic solvents other than alcohol were also used. In addition,small amounts of ethyl silicate, HNO, and HCl were also incorporated inthe solutions. The No. 14 solution also contained a small amount of BiClThe other ingredients were the same as those used in No. 3.

The surfaces of each glass sheet 3 mm thick and 30 by 30 cm were coatedin the same manner as in Examples 1 and 1], whereby a film about 500 Athick was formed on either surface.

lt was found that the glass sample designated No. 13 was substantiallycomparable to the No. 3 glass sample in optical, mechanical and chemicalproperties.

The No. 14 sample was substantially identical with No. 3 and No. 13samples in optical, mechanical and chemical characteristics, but itsspectral transmission curve revealed a decrease in transmission in thewavelength region shorter than 360 mp.

Thus, there was a drop of about 5 percent at 340 mu, thus attesting to ashielding effect against ultraviolet light.

What is claimed is:

1. A method of producing a heat-reflecting glass, which comprises thesteps of dissolving in an organic solvent selected from the groupconsisting of alcohols, acetone, esters, alicylic compounds and aromaticcompounds a compound capable of forming metallic palladium on heatingand a compound capable of forming on heating a metallic oxide having arefractive index higher than that of the glass, the proportion of thefirstmentioned compound and the other compound in the solution beingfrom 2:98 to 60:40, by weight, calculated as metallic palladium andmetallic oxide, respectively, and the concentration of thefirst-mentioned compound being at least 0.4 g/l, calculated as metallicpalladium; coating a surface of a glass substrate with the solution; andheating the coated glass to a temperature sufficient to decompose thefirst-mentioned compound until a light-transmissive film having athickness of about A to 1,500 A and consisting essentially of a matrixof the metallic oxide and colloidal particles of the metallic palladiumuniformly dispersed in the metallic oxide matrix in a microscopicallydivided state is formed on the substrate.

2. A heat-reflecting glass manufactured by the method of claim 1.

3. The method as claimed in claim 1, wherein said compound capable offorming on heating a metallic oxide having a refractive index higherthan the glass is a soluble compound selected from the group consistingof the halides, nitrates,

metallic acid esters, sulfates and acetates of Ti, Ta, W, Zr, Th, Sn andNb.

4. The method as claimed in claim 1, wherein the concentration of thefirst-mentioned compound in between about 2 g/l and 20 g/l.

5. A method of producing a heat-reflecting galss, which comprises thesteps of dissolving in an organic solvent selected from the groupconsisting of alcohols, acetone, esters, alicylic compounds and aromaticcompounds a first compound capable of forming metallic palladium onheating, a second compound capable of forming metallic gold on heating,and a third compound capable of forming on heating a metallic oxidehaving a refractive index higher than that of the glass, the proportionof the combined first and second compounds and the third compound in thesolution being from 2:98 to 60:40, by weight, calculated as combinedmetallic palladium and gold and as metallic oxide, respectively, theconcentration of the first compound being at least 0.4 g/l, calculatedas metallic palladium, and the concentration of the second compoundbeing 0.1 to 20 times, by weight, the concentration of the firstcompound, calculated as metallic palladium and metallic gold,respectively; coating the surface of a glass substrate with thesolution; and heating the coated glass to a temperature sufficient todecompose the first and second compounds until a light-transmissive filmhaving a thickness of about 100 A to 1,500 A and consisting essentiallyof a matrix of the metallic oxide and colloidal particles of themetallic palladium and metallic gold uniformly dispersed in the metallicoxide matrix in a microscopically divided state is formed on thesubstrate.

6. The method as claimed in claim 5, wherein said compound capable offorming on heating a metallic oxide having a refractive index higherthan glass is a soluble compound selected from the group consisting ofthe halides, nitrates, metallic acid esters, sulfates and acetates ofTi, Ta, W, Zr, Th, Sn and Nb.

UNITED ST PATENT OFFICE CERTIFICATE OF CORRECTION Pa tent No. 3 660, 137Dated May 2 1972 Inventor(s) Shigemasa Furuuchi et a].

It is certified that error a opears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

On the title page, after "'72" insert:-

(73) Assignee: Asahi Glass Co. Ltd. of Tokyo Japan Signed and sealedthis 31st day of October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOITSGHALK Attesting Officer Commissionerof Patents F ORM PO-105O (10-69) USCOMM-DC 6O376-P69 U,$. GOVERNMENTPRINTING OFFICE I969 oass334 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Pa tent No. 3, 660, 137 Dated May 2 1972 Inventor(s)Shigemasa Furuuchi et al It is certified that error appears in theabove-j-identified patent and that said Letters Patent are herebycorrected as shown below:

On the title page, after "72" insert:-

(73) Assignee: Asahi Glass Co. Ltd. of Tokyo Japan Signed and sealedthis 31st day of October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOT'ISCHALK Attesting Officer Commissionerof Patents FORM F'O-105O (10-69) USCQMM-DC 50375-p5 *1 us. GOVERNMENTPRINTING OFFICE: I969 0-365-334

2. A heat-reflecting glass manufactured by the method of claim
 3. Themethod as claimed in claim 1, wherein said compound capable of formingon heating a metallic oxide having a refractive index higher than theglass is a soluble compound selected from the group consisting of thehalides, nitrates, metallic acid esters, sulfates and acetates of Ti,Ta, W, Zr, Th, Sn and Nb.
 4. The method as claimed in claim 1, whereinthe concentration of the first-mentioned compound in between about 2 g/land 20 g/l.
 5. A method of producing a heat-reflecting galss, whichcomprises the steps of dissolving in an organic solvent selected fromthe group consisting of alcohols, acetone, esters, alicylic compoundsand aromatic compounds a first compound capable of forming metallicpalladium on heating, a second compound capable of forming metallic goldon heating, and a third compound capable of forming on heating ametallic oxide having a refractive index higher than that of the glass,the proportion of the combined first and second compounds and the thirdcompound in the solution being from 2:98 to 60:40, by weight, calculatedas combined metallic palladium and gold and as metallic oxide,respectively, the concentration of the first compound being at least 0.4g/l, calculated as metallic palladium, and the concentration of thesecond compound being 0.1 to 20 times, by weight, the concentration ofthe first compound, calculated as metallic palladium and metallic gold,respectively; coating the surface of a glass substrate With thesolution; and heating the coated glass to a temperature sufficient todecompose the first and second compounds until a light-transmissive filmhaving a thickness of about 100 A to 1,500 A and consisting essentiallyof a matrix of the metallic oxide and colloidal particles of themetallic palladium and metallic gold uniformly dispersed in the metallicoxide matrix in a microscopically divided state is formed on thesubstrate.
 6. The method as claimed in claim 5, wherein said compoundcapable of forming on heating a metallic oxide having a refractive indexhigher than glass is a soluble compound selected from the groupconsisting of the halides, nitrates, metallic acid esters, sulfates andacetates of Ti, Ta, W, Zr, Th, Sn and Nb.